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United States Patent |
6,090,109
|
Lands
,   et al.
|
July 18, 2000
|
Laparoscopic bipolar electrosurgical instrument
Abstract
A laparoscopic bipolar electrosurgical instrument can apply a large closure
force between its jaws without damaging the small yoke assembly. The
instrument comprises: a first jaw having a first flange with a first slot,
and a second jaw having a second flange with a second slot, wherein the
first and second jaws are located at a distal end of the instrument and
comprise an electrically conductive material for conducting bipolar
electrosurgical current therebetween; a yoke attached to a pushrod and
positioned to electrically insulate the first flange from the second
flange, the yoke having a first side facing the first flange and a second
side facing the second flange, the yoke further comprising a first
shoulder and a second shoulder; a first pin located on the first side and
movably engaged with the first slot; a second pin located on the second
side and movably engaged with the second slot; the first slot and the
second slot shaped such that an angle, subtended by the first and second
jaws, decreases with distal motion of the pushrod, and first and second
cul-de-sacs positioned respectively in the first and second slots to
relieve shear stresses on the first and second pins approximately when the
first and second shoulders respectively engage the first and second
flanges to provide a closure force between the first and second jaws.
Inventors:
|
Lands; Michael John (Clearwater, FL);
Lukianow; Stephen Wade (Boulder, CO);
Loeffler; Donald Robert (Louisville, CO);
Cunnigham; James Steven (Boulder, CO);
Lawes; Kate Ryland (Boulder, CO);
Trimberger, II; Daniel Lee (Greeley, CO);
Mitchell; Mathew Erle (Boulder, CO);
Kennedy; Jenifer Serafin (Boulder, CO)
|
Assignee:
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Sherwood Services AG (Schwerstrasse, CH)
|
Appl. No.:
|
970472 |
Filed:
|
November 14, 1997 |
Intern'l Class: |
A61B 017/39 |
Field of Search: |
606/46,48-52,170,207,208
|
References Cited
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|
Foreign Patent Documents |
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| |
Other References
Bergdahl et al., Studies on Coagulation and the Development of an Automatic
Computerized Bipolar Coagulator, J. Neurosurg. vol. 75, Jul. 1991 pp
148-151.
Sigel et al., The Mechanism of Blood Vessel Closure by High Frequency
Electrocoagulation, Surgery & Gynecology and Obstetrics, Oct. 1965 pp.
823-831.
|
Primary Examiner: Cohen; Lee
Claims
What is claimed is:
1. A laparoscopic bipolar electrosurgical instrument comprising:
a first jaw having a first flange with a first slot, and a second jaw
having a second flange with a second slot, wherein the first and second
jaws are located at a distal end of the instrument and comprise an
electrically conductive material for conducting bipolar electrosurgical
current therebetween;
an electrically conductive pushrod for connecting the first jaw to a source
of electrosurgical energy;
an electrically conductive tube for connecting the second jaw to a source
of electrosurgical energy;
a yoke attached to the pushrod and positioned to electrically insulate the
first flange from the second flange, the yoke having a first side facing
the first flange and a second side facing the second flange, the yoke
further comprising a first shoulder and a second shoulder;
a first pin located on the first side and movably engaged with the first
slot;
a second pin located on the second side and movably engaged with the second
slot;
the first slot and the second slot shaped such that an angle, subtended by
the first and second jaws, decreases with distal motion of the pushrod;
first and second cul-de-sacs positioned respectively in the first and
second slots to relieve shear stresses on the first and second pins
approximately when the first and second shoulders respectively engage the
first and second flanges to provide a closure force between the first and
second jaws; and
a handle attached to the pushrod for imparting movement to the yoke.
2. The laparoscopic bipolar electrosurgical instrument of claim 1 wherein:
the electrically conductive tube surrounds at least a portion of the
pushrod, and
an electrically insulative layer is disposed between the tube and the
pushrod capable of supporting an electrosurgical alternating potential
across the tube and the pushrod.
3. The laparoscopic bipolar electrosurgical instrument of claim 2 further
comprising:
an inner nose piece electrically connected to the pushrod, and
an outer nose piece electrically connected to the tube, wherein the inner
nose piece and the outer nose piece capture the yoke, along with the first
and second flanges, to conduct bipolar electrosurgical current to the
first and second jaws.
4. The laparoscopic bipolar electrosurgical instrument of claim 3 further
comprising an electrical spring contact between the pushrod and the inner
nose piece to provide electrical continuity therebetween.
5. The laparoscopic bipolar electrosurgical instrument of claim 1 further
comprising ridges in each of the first and second jaws.
6. The laparoscopic bipolar electrosurgical instrument of claim 1 wherein
each of the first and second jaws has a seal surface with width and a
length, and wherein at least one location along the length has a width
such that the closure force in grams divided by the width in millimeters
is in the range of 400 to 650.
7. The laparoscopic bipolar electrosurgical instrument of claim 6, wherein
the width of each seal surface is tapered along its respective length.
8. The bipolar electrosurgical instrument according to claim 7, wherein the
closure force divided by the width is approximately constant along the
length for each of the first and second jaws.
9. A laparoscopic bipolar electrosurgical instrument comprising:
a first jaw having a first flange with a first slot, and a second jaw
having a second flange with a second slot, wherein the first and second
jaws are located at a distal end of the instrument and comprise an
electrically conductive material for conducting bipolar electrosurgical
current therebetween;
an electrically conductive pushrod for connecting the first jaw to a source
of electrosurgical energy;
an electrically conductive tube for connecting the second jaw to a source
of electrosurgical energy;
a yoke attached to the pushrod and electrically insulating the first flange
from the second flange, the yoke having a first side facing the first
flange and a second side facing the second flange, the yoke further
comprising a first shoulder and a second shoulder;
a first pin located on the first side and movably engaged with the first
slot;
a second pin located on the second side and movably engaged with the second
slot;
the first slot and the second slot shaped such that a subtended angle
between the first and second jaws decreases with distal motion of the
pushrod;
first and second cul-de-sacs positioned respectively in the first and
second slots to relieve shear stresses on the first and second pins at the
subtended angle approximately when the first and second shoulders engage
the first and second flanges,
the electrically conductive tube having an outer surface and a length,
wherein the tube surrounds at least a portion of the pushrod; an
electrically insulative layer between the tube and the pushrod capable of
supporting an electrosurgical alternating potential across the tube and
the pushrod;
an inner nose piece electrically connected to the pushrod;
an outer nose piece electrically connected to the tube, wherein the inner
nose piece and the outer nose piece capture the yoke along with the first
and second flanges to conduct bipolar electrosurgical current to the first
and second jaws;
an electrical spring contact between the pushrod and the inner nose piece
to provide electrical continuity therebetween; and
a handle attached to the pushrod for imparting movement to the yoke.
10. A method of making a laparoscopic bipolar instrument comprising the
following steps:
forming a first jaw having a first flange with a first slot, and a second
jaw having a second flange with a second slot, wherein the first and
second jaws are located at a distal end of the instrument and comprise an
electrically conductive material for conducting bipolar electrosurgical
current therebetween;
providing an electrically conductive pushrod for connecting the first jaw
to a source of electrosurgical energy;
providing an electrically conductive tube for connecting the second jaw to
a source of electrosurgical energy;
attaching a yoke to the pushrod;
electrically insulating the first flange from the second flange with the
yoke, the yoke having a first side facing the first flange and a second
side facing the second flange, the yoke further comprising a first
shoulder and a second shoulder;
engaging a first pin located on the first side with the first slot;
engaging a second pin located on the second side with the second slot;
shaping the first slot and the second slot such that a subtended angle
between the first and second jaws decreases with the distal motion of the
pushrod;
positioning first and second cul-de-sacs respectively in the first and
second slots to relieve shear stresses on the first and second pins at the
subtended angle approximately wherein the first and second shoulders
engage the first and second flanges; and
providing a handle for imparting movement of the yoke.
11. The method of making a laparoscopic bipolar electrosurgical instrument
of claim 10 further comprising the steps of:
surrounding at least a portion of the pushrod with the electrically
conductive tube having an outer surface and a length, and
electrically insulating the tube from the pushrod.
12. The method of making a laparoscopic bipolar electrosurgical instrument
of claim 11 further comprising the steps of:
electrically connecting an inner nose piece to the pushrod, and
electrically connecting an outer nose piece to the tube, wherein the inner
nose piece and the outer nose piece capture the yoke along with the first
and second flanges to conduct bipolar electrosurgical current to the first
and second jaws.
13. The method of making a laparoscopic bipolar electrosurgical instrument
of claim 12 further comprising the step of electrically connecting the
pushrod and the inner nose piece with a spring contact.
14. The method of making a laparoscopic bipolar electrosurgical instrument
of claim 10, wherein the first and second jaws each has a length and a
width and oppose each other with a closure force, the method further
comprising the step of tapering the width along the length of each of the
first and second jaws.
15. The method of making a laparoscopic bipolar electrosurgical instrument
of claim 14 further comprising the step of wherein the closure force in
grams divided by the width in millimeters is in the range of 400 to 650.
16. The method of making a laparoscopic bipolar electrosurgical instrument
of claim 14 further comprising the step of, wherein the width of the first
and second jaws is tapered along its respective length.
17. The method of making a laparoscopic bipolar electrosurgical instrument
of claim 16 further comprising the step of, wherein the closure force
divided by the width is approximately constant along the length for each
of the first and second jaws.
18. A laparoscopic bipolar endoscopic instrument, comprising:
first and second jaw members pivotally attached in opposing relation
relative to one another, each of the jaw members including a flange which
extends therefrom and the jaw members being relatively movable from a
first open position wherein the jaw members are disposed in spaced
relation relative to one another to a second clamping position wherein the
jaw members cooperate to grasp tissue therebetween,
an electrically conductive push rod for connecting the first jaw member to
a first pole and an electrically conductive tube for connecting the second
jaw member to a second pole such that the jaw members are capable of
conducting bipolar energy through the tissue held therebetween;
a yoke attached to a distal end of the push rod and attached between the
jaw members, the yoke includes a pair of pins which cooperate with a
corresponding pair of slots in a cam-follower-like manner to impart
movement of the jaw members from the first and second positions;
a pair of shoulder portions attached to the yoke which are dimensioned to
abut the flanges of the jaw members when the jaw members are moved into
the second position to relieve shear stresses on the pins during clamping
and sealing of the tissue; and
a handle attached to the push rod for imparting movement to the yoke.
Description
FIELD OF THE INVENTION
This relates to an electrosurgical instrument for performing laparoscopic
surgical procedures, and more particularly to a laparoscopic
electrosurgical instrument that is capable of grasping vessels and
vascular tissue with sufficient force between two bipolar jaws to seal the
vessel or vascular tissue.
BACKGROUND OF THE DISCLOSURE
Laparoscopic surgical instruments are used to perform surgical operation
without making large incisions in the patient. The laparoscopic
instruments are inserted into the patient through a cannula, or port, that
has been made with a trocar. Typical sizes for cannulas range from three
millimeters to twelve millimeters. Smaller cannulas are usually preferred,
and this presents a design challenge to instrument manufacturers who must
find ways to make surgical instruments that fit through the cannulas.
Certain surgical procedures require cutting blood vessels or vascular
tissue. This sometimes presents a problem for surgeons because it is
difficult to suture blood vessels using laparoscopic tools. Very small
blood vessels, in the range below two millimeters in diameter, can often
be closed using standard electrosurgical techniques. If a larger vessel is
severed, it may be necessary for the surgeon to convert the laparoscopic
procedure into an open-surgical procedure and thereby abandon the benefits
of laparoscopy.
Several journal articles have disclosed methods for sealing small blood
vessels using electrosurgery. An article entitled Studies on Coagulation
and the Development of an Automatic Computerized Bipolar Coagulator, J.
Neurosurg., Volume 75, July 1991, describes a bipolar coagulator which is
used to seal small blood vessels. The article states that it was not
possible to safely coagulate arteries with a diameter larger than 2 to 2.5
mm. A second article is entitled Automatically Controlled Bipolar
Electrocoagulation--"COA-COMP", Neurosurg. Rev. (1984), pp. 187-190. This
article describes a method for terminating electrosurgical power to the
vessel so that charring of the vessel walls can be avoided.
It has been recently determined that electrosurgical methods may be able to
seal larger vessels using an appropriate electrosurgical power curve,
coupled with an instrument capable of applying a large closure force to
the vessel walls. It is thought that the process of coagulating small
vessels is fundamentally different than electrosurgical vessel sealing.
Coagulation is defined as a process of desiccating tissue wherein the
tissue cells are ruptured and dried. Vessel sealing is defined as the
process of liquefying the collagen in the tissue so that it crosslinks and
reforms into a fused mass. Thus, coagulation of small vessels is
sufficient to permanently close them. Larger vessels need to be sealed to
assure permanent closure.
It would be desirable to have a surgical tool capable of applying
electrosurgical energy, capable of applying a large closure force to the
vessel walls, and also capable of fitting through a cannula. A large
closure force between the jaws typically requires a large moment about the
pivot for each jaw. This presents a challenge because the first and second
pins have a small moment arm with respect to the pivot of each jaw. A
large force, coupled with a small moment arm, is undesirable because the
large forces may shear the first and second pins. It is also undesirable
to increase the moment arm of the first and second pins because the
physical size of the yoke might not fit through a cannula.
Several bipolar laparoscopic instruments are known. For example, U.S. Pat.
No. 3,938,527 discloses a bipolar laparoscopic instrument for tubal
cauterization. U.S. Pat. No. 5,250,047 discloses a bipolar laparoscopic
instrument with a replaceable electrode tip assembly. U.S. Pat. No.
5,445,638 discloses a bipolar coagulation and cutting forceps with first
and second conductors extending from the distal end. U.S. Pat. No.
5,391,166 discloses a bipolar endoscopic instrument having a detachable
working end. U.S. Pat. No. 5,342,359 discloses a bipolar coagulation
device.
The present invention solves the problem of providing a large closure force
between the jaws of a laparoscopic bipolar electrosurgical instrument,
using a compact design that fits through a cannula, without risking
structural failure of the instrument yoke.
SUMMARY OF THE INVENTION
The present invention is an instrument for applying bipolar electrosurgical
current to tissue in a laparoscopic operation with the added benefit of
providing a large closure force between the instrument jaws. The large
closure force may be particularly useful for vessel sealing operations. An
advantage of the present invention is that tissue can be grasped and
clamped with a relatively large closure force without damage to the yoke.
The yoke is capable of transmitting the large closure force to the
instrument jaws while being small enough to fit through a cannula.
The laparoscopic bipolar electrosurgical instrument comprises first and
second jaws having, respectively, first and second flanges with first and
second slots. The instrument is electrically connected to an
electrosurgical generator, and conducts bipolar electrosurgical current to
the first and second jaws. A yoke is attached to a pushrod and positioned
to electrically insulate the first flange from the second flange. First
and second pins on the yoke are designed to engage the first and second
slots, respectively, in a cam-follower arrangement that opens and closes
the jaws with linear motion of the yoke. The yoke is preferably a "push
yoke" which means that linear motion of the yoke in the direction of the
distal end of the instrument will cause the jaws to close together.
The yoke has first and second shoulders that are spaced apart from the
first and second flanges until the jaws are in close arcuate proximity to
each other. At that point, the first and second shoulders engage the first
and second flanges, whereby further distal motion of the yoke applies a
force to the first and second flanges that creates a moment about the
pivot of each jaw. In general, the cam-follower arrangement of pins and
slots may be designed to provide coarse motion of the jaws with relatively
small forces. Large closure forces, once the jaws are relatively close
together, may be obtained by pressing the shoulders against the flanges.
The first and second pins move into cul-de-sacs in the first and second
slots to protect them from large shear stresses when the shoulders are
applying relatively large forces to the flanges. Thus, the first and
second pins may be made from an electrically insulative material that is
not designed to handle large shear stresses, large closure forces may be
obtained, and the entire assembly may be compact and fit through a
cannula.
A method of making the laparoscopic bipolar electrosurgical instrument is
described, comprising the following steps: forming a first jaw having a
first flange with a first slot, and a second jaw having a second flange
with a second slot; attaching a yoke to a pushrod; electrically insulating
the first flange from the second flange with the yoke; engaging first and
second pins with the first and second slots; positioning first and second
cul-de-sacs respectively in the first and second slots to relieve shear
stresses on the first and second pins at a subtended angle approximately
wherein first and second shoulders engage the first and second flanges.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a laparoscopic bipolar electrosurgical
instrument.
FIG. 2 is a perspective view of the distal end and jaws of the instrument
in FIG. 1.
FIG. 3 is an exploded view of the distal end shown in FIG. 2.
FIG. 4 is perspective view of the distal end of the instrument with the
jaws removed.
FIG. 5 is another perspective of FIG. 4.
FIG. 6 is a side view of an electrical spring contact.
FIG. 7 is a front view of the spring contact shown in FIG. 6.
DETAILED DESCRIPTION OF THE INVENTION
A laparoscopic bipolar electrosurgical instrument 10 is shown in FIG. 1.
The instrument 10 has a proximal end 11 with a handle 14 for holding and
manipulating the instrument 10. A distal end 12 on the instrument 10 is
used for surgical manipulation of tissue. The instrument 10 comprises an
elongate tube 13 that is sized to fit through a cannula for laparoscopic
operations, and in different embodiments may be sized to fit through
either a five or seven millimeter cannula.
A portion of the distal end 12 of the instrument 10 is shown in FIG. 2. A
first jaw 15 and a second jaw 16 are shown in an open position. An angle
.alpha. is subtended by the jaws 15 and 16. Closing of the jaws 15 and 16
is defined as a reduction of the angle .alpha. subtended by the jaws 15
and 16. Similarly, opening of the jaws 15 and 16 is defined as an
enlargement of the angle .alpha.. The angle .alpha. is zero when the jaws
15 and 16 are closed together. The center of rotation for the first jaws
15 is at the first pivot 41, and the center of rotation for the second jaw
16 is at the second pivot 42. The first pivot 41 is located on an outer
nose piece 32, and inner nose piece 31, and fits in a second pivot hole 44
located on the second flange 20.
Pieces that comprise the distal end 12 of the instrument 10 are shown in an
exploded view in FIG. 3. The first jaw 15 and the second jaw 16 are shown
separated from a yoke 17. The first jaw 15 has a first flange 18 and a
first slot 19 therewithin. The second jaw 16 has a second flange 20 and a
second slot 21 therewithin. Each jaw 15 and 16 is preferably formed from a
single piece of stainless steel or other electrically conductive material.
Referring again to FIG. 3, the yoke 17 is attached to a pushrod 22. The
yoke 17 is preferably formed from an electrically insulative material such
as plastic. A first side 23 of the yoke 17 faces the first flange 18. A
second side 24 of the yoke 17 faces the second flange 20. When the yoke 17
is positioned between the flanges 18 and 20, the yoke 17 also acts to
electrically insulate the first jaw 15 from the second jaw 16. In this
manner, bipolar electrosurgical current can be conducted through tissue
grasped by the jaws 15 and 16 without short circuiting between the flanges
18 and 20.
A first pin 25 is located on the first side 23 to movably engage with the
first slot 19. Similarly, a second pin 26 is located on the second side 24
to movably engage with the second slot 21. Each pin and slot combination
works as a cam-follower mechanical linkage. Motion of the pushrod 22 moves
the yoke 17 causing pins 25 and 26 to slide within their respective slots
19 and 21. The slots 19 and 21 are angled with respect to the distal ends
of the jaws 15 and 16 such that the jaws 15 and 16 move in an arcuate
fashion toward and away from each other. The pins 25 and 26 are different
from the pivots 41 and 42. The pins 25 and 26 provide a force against the
walls of the slots 19 and 21, creating a moment about the pivots 41 and
42.
The slots 19 and 21 are arranged such that distal motion of the pushrod 22
causes the jaws 15 and 16 to move together. Distal motion of the pushrod
22 is defined as motion in the direction of the distal end 12 of the
instrument 10. Once the jaws 15 and 16 are closed together, the present
invention holds the jaws 15 and 16 together with a compressive force on
the pushrod 22.
One of the advantages of this invention is that shear forces on the pins 25
and 26 can be offloaded to prevent mechanical failure when large forces
are being transmitted to the jaws 15 and 16. Each slot 19 and 20 has a
cul-de-sac 27 and 28, respectively, as shown in FIG. 3. The first
cul-de-sac 27 is an enlargement of the first slot 19 near its distal end.
The second cul-de-sac 28 is an enlargement of the second slot 21 near its
distal end. The cam-follower motion of the pins 25 and 26 in the slots 19
and 21 will bring the pins 25 and 26 into their respective cul-de-sac 27
and 28. This position of the pins 25 and 26 leaves a very small moment arm
between the pins 25 and 26 and the pivots 41 and 42. The yoke 17 has
shoulders 29 and 30 that can provide a relatively large moment about the
pivots 41 and 42 to effect a high closure force between the jaws 15 and 16
without a high shear forces on the pins 25 and 26, as described below.
Once the pins 25 and 26 are in the cul-de-sacs 27 and 28, the force from
the yoke is transmitted to the flanges 18 and 20 by a first shoulder 29
and a second shoulder 30. The shoulders 29 and 30 abut the proximal end of
the flanges 18 and 20 to cause the jaws 15 and 16 to close together. The
pivots 41 and 42 are preferably made of metal and can withstand relatively
high shear forces. In contrast, pins 25 and 26 are preferably made of
plastic and will break under relatively high shear forces. Thus, the
shoulders 29 and 30 provide a moment about the pivots 41 and 42, thereby
avoiding the necessity of applying high shear forces to the pins 25 and 26
when the moment arm from the pins 25 and 26 would be small. There is an
angle .alpha. at which the pins 25 and 26 enter their respective
cul-de-sacs 27 and 28 and the shoulders 29 and 30 abut the flanges 18 and
20. The angle a at which the forgoing occurs is preferably around three
degrees.
The bipolar electrosurgical instrument 10 has first and second poles of
alternating potential that are conducted along the instrument 10 and
through tissue that is grasped between the jaws 15 and 16. The first pole
is conducted from the proximal end 11 toward the distal end 12 along the
pushrod 22. The second pole is conducted from the proximal end 11 toward
the distal end 12 along the tube 13. The outer surface of the tube 13 is
preferably coated with an electrically insulative material. There is also
preferably an electrically insulative barrier between the pushrod 22 and
the tube 13 to prevent short circuits in the instrument 10.
In the preferred embodiment, the distal end of the instrument 10 comprises
an inner nose piece 31 and an outer nose piece 32, as shown in FIG. 2. The
inner nose piece 31 is electrically connected with the pushrod 22, while
the outer nose piece is electrically connected with the tube 13. The inner
nose piece 31 and the outer nose piece 32 capture the yoke 17, along with
the first and second flanges 18 and 20, as shown in FIG. 2. The yoke 17
moves axially, along an axis defined by the tube, in a space between the
inner and outer nose pieces 31 and 32. A spacer stake 33 maintains the
separation of the nose pieces 31 and 32 at their distal ends. The nose
pieces 31 and 32 provide lateral support for the flanges 18 and 20 to help
ensure that the pins 25 and 26 remain within the slots 19 and 21.
The preferred embodiment also comprises an inner insulator 34 and an outer
insulator 35 for maintaining electrical insulation between the poles. The
outer insulator 35 is seated between the tube 13 and the inner nose 31, as
shown in FIGS. 2 and 4. The inner insulator 34 is seated between the tube
13 and the pushrod 22. In this manner, the outer nose piece 32 can provide
electrical continuity between the tube 13 and the second jaw 16, while the
inner nose piece 34 can provide electrical continuity between the pushrod
22 and the first jaw 15. Since the pushrod 22 is slidably mounted within
the tube 13, the preferred embodiment has a spring contact 36, as shown in
FIGS. 6 and 7, mounted on the pushrod 22 to maintain an electrical
connection with the inner nose piece 34 during axial motion.
The first and second jaws 15 and 16 each have ridges 37 and 38 at their
distal ends that preferably nest together. The jaws 15 and 16 also have
seal surfaces 39 and 40, as shown in FIG. 2. The width of the seal
surfaces 39 and 40 is a parameter that affects the quality of the surgical
outcome. The closure force between the jaws 15 and 16 varies along the
length of the seal surfaces 39 and 40, with the largest force at the
distal tip and the smallest force at the proximal end of the seal surfaces
39 and 40. It has been found through experimentation that good vessel
sealing results are obtained when the closure force in grams divided by
the width in millimeters is in the range of 400 to 650. Since the closure
force varies with the length of the seal surfaces 39 and 40, it has been
found to be advantageous to taper the width of the seal surfaces 39 and 40
along their length, with the widest width at the proximal end and the
narrowest width at the distal end. This design allows the jaws 15 and 16
to apply a relatively constant closure force per unit width, preferably
525 grams per millimeter width.
A method of making a laparoscopic bipolar electrosurgical instrument 10 is
also herein described. The method comprises the step of forming a first
jaw 15 having a first flange 18 with a first slot 19, and a second jaw 16
having a second flange 20 with a second slot 21. The jaws 15 and 16 are
preferably formed in a casting process, although it is also possible to
machine the jaws 15 and 16 from stock. The casting process may include
injecting powdered metal under pressure into a mold, and then applying
heat.
Other steps in the method include attaching a yoke 17 to a pushrod 22, and
electrically insulating the first flange 18 from the second flange 20 with
the yoke 17. The yoke 17 is preferably an injection molded plastic part
with features including a first shoulder 29 and a second shoulder 30.
During assembly of the distal portion of the instrument 10, steps in the
method include engaging a first pin I5 with the first slot 19, and
engaging a second pin 26 with the second slot 21. The slots 19 and 21 are
shaped such that a subtended angle .alpha. between the first and second
jaws 15 and 16 decreases with distal motion of the pushrod 17, and the
slots 19 and 20 are formed with cul-de-sacs 27 and 28 positioned to
relieve shear stresses on the first and second pins 25 and 26 at the
subtended angle .alpha. approximately wherein the first and second
shoulders 29 and 30 engage the first and second flanges 18 and 20.
Further steps in the method comprise: surrounding at least a portion of the
pushrod 22 with an electrically conductive tube 13; electrically
insulating the tube 13 from the pushrod 22; electrically connecting an
inner nose piece 31 to the pushrod 22, and electrically connecting an
outer nose piece 32 to the tube 13, wherein the inner nose piece 31 and
the outer nose piece 32 capture the yoke 17 along with the first and
second flanges 18 and 20 to conduct bipolar electrosurgical current to the
first and second jaws 15 and 16. In the preferred embodiment, there is a
step of electrically connecting the pushrod 22 and the inner nose piece 31
with a spring contact 36.
The method of making the instrument 10, in some embodiments, includes the
steps of tapering the width of the seal surfaces 39 and 40 along the
length of each of the first and secondjaws 15 and 16.
While a particular preferred embodiment has been illustrated and described,
the scope of protection sought is in the claims that follow.
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